to wire it unseen. However, you can go buy cheap plastic cable covers to hide the cable as you run it along the wall, ceiling, and floorboards, and then paint the covers the same color as your wall/ceiling. It won't look bad, just not as clean.

As far as "screen" is concerned, depends on how much you care about picture quality. We watch a lot of movies and sports, so we have a nice dedicated screen. The wall works, but a screen is much nicer.